Create a Plan where the customers will pay you in advance.
Example: Pay 11000 and Get 4000 wallet credits for 3 Months.
The customers will get some extra value to their wallet after paying you up front for the plan.
Like in the above example the customer will get 12000 in 3 months after paying 11000 as an advance for the plan.
The user will get the monthly credits set by the Admin against the plan purchased automatically to their wallet.
This will also boost the number of loyal customers to the platform.